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dccp: Return-value convention of hc_tx_send_packet() 

This patch reorganises the return value convention of the CCID TX sending
function, to permit more flexible schemes, as required by subsequent patches.

Currently the convention is
 * values < 0     mean error,
 * a value == 0   means "send now", and
 * a value x > 0  means "send in x milliseconds".

The patch provides symbolic constants and a function to interpret return values.

In addition, it caps the maximum positive return value to 0xFFFF milliseconds,
corresponding to 65.535 seconds.  This is possible since in CCID-3/4 the
maximum possible inter-packet gap is fixed at t_mbi = 64 sec.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gerrit Renker 2010-10-27 19:16:25 +00:00 committed by David S. Miller
parent de7fe7874d
commit fe84f4140f
2 changed files with 37 additions and 9 deletions
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34
net/dccp/ccid.h
View File

@ -134,13 +134,41 @@ static inline int ccid_get_current_tx_ccid(struct dccp_sock *dp)
extern void ccid_hc_rx_delete(struct ccid *ccid, struct sock *sk);
extern void ccid_hc_tx_delete(struct ccid *ccid, struct sock *sk);
/*
* Congestion control of queued data packets via CCID decision.
*
* The TX CCID performs its congestion-control by indicating whether and when a
* queued packet may be sent, using the return code of ccid_hc_tx_send_packet().
* The following modes are supported via the symbolic constants below:
* - timer-based pacing (CCID returns a delay value in milliseconds);
* - autonomous dequeueing (CCID internally schedules dccps_xmitlet).
*/
enum ccid_dequeueing_decision {
CCID_PACKET_SEND_AT_ONCE = 0x00000, /* "green light": no delay */
CCID_PACKET_DELAY_MAX = 0x0FFFF, /* maximum delay in msecs */
CCID_PACKET_DELAY = 0x10000, /* CCID msec-delay mode */
CCID_PACKET_WILL_DEQUEUE_LATER = 0x20000, /* CCID autonomous mode */
CCID_PACKET_ERR = 0xF0000, /* error condition */
};
static inline int ccid_packet_dequeue_eval(const int return_code)
{
if (return_code < 0)
return CCID_PACKET_ERR;
if (return_code == 0)
return CCID_PACKET_SEND_AT_ONCE;
if (return_code <= CCID_PACKET_DELAY_MAX)
return CCID_PACKET_DELAY;
return return_code;
}
static inline int ccid_hc_tx_send_packet(struct ccid *ccid, struct sock *sk,
struct sk_buff *skb)
{
int rc = 0;
if (ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
rc = ccid->ccid_ops->ccid_hc_tx_send_packet(sk, skb);
return rc;
return ccid->ccid_ops->ccid_hc_tx_send_packet(sk, skb);
return CCID_PACKET_SEND_AT_ONCE;
}
static inline void ccid_hc_tx_packet_sent(struct ccid *ccid, struct sock *sk,

12
net/dccp/ccids/ccid3.c
View File

@ -268,11 +268,11 @@ out:
sock_put(sk);
}
/*
* returns
* > 0: delay (in msecs) that should pass before actually sending
* = 0: can send immediately
* < 0: error condition; do not send packet
/**
* ccid3_hc_tx_send_packet - Delay-based dequeueing of TX packets
* @skb: next packet candidate to send on @sk
* This function uses the convention of ccid_packet_dequeue_eval() and
* returns a millisecond-delay value between 0 and t_mbi = 64000 msec.
*/
static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
{
@ -348,7 +348,7 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
/* set the nominal send time for the next following packet */
hc->tx_t_nom = ktime_add_us(hc->tx_t_nom, hc->tx_t_ipi);
return 0;
return CCID_PACKET_SEND_AT_ONCE;
}
static void ccid3_hc_tx_packet_sent(struct sock *sk, unsigned int len)